1. Field of the Invention
The present invention relates to an optical pickup device used in an optical information recording/playback apparatus, and more particularly to a method of fixing an optical detector thereof.
2. Description of the Background Art
Information recorded on an optical disk as data of digital signals is read by a playback device, and the read operation of the information is performed in an optical pickup device included in the playback device. The optical pickup device, which irradiates the optical disk with an irradiation light emitted from a laser optical source and detects the reflected light from the optical disk to convert it into an electrical signal, has an optical instrument positioned with extremely high accuracy.
FIG. 10 is a plan view showing a background-art optical pickup device disclosed in Japanese Patent Application Laid-Open Gazette No. 8-7535. In FIG. 10, reference numeral 101 denotes an optical detector which receives a light signal which is a reflected light from an optical disk (in the present description, for convenience of discussion, the reflected light from an optical disk is sometimes referred to simply as “reflected light”) and converts the light signal into an electrical signal corresponding thereto, and reference sign 101a denotes a lead portion for outputting the electrical signal from the optical detector 101. Reference numeral 102 denotes a flexible substrate (hereinafter, referred to as “FPC”) having a conductor portion 102a to which the electrical signal outputted from the lead portion 101a of the optical detector 101 is inputted, and the lead portion 101a is fixed to the conductor portion 102a by soldering with a solder portion 103. Numeral 104 denotes an adjustment board made of, e.g., iron onto which the FPC 102 is attached with a not-shown adhesive layer, and numeral 105 denotes an optical unit in which not-shown optical parts and the like are provided. Numeral 106 denotes a first adhesive of UV light hardening type which is applied in dots and hardened for quick hardening. Numeral 107 denotes a second adhesive made of two-part epoxy, which is applied and hardened on the first adhesive 106 so as to cover it and further around the adjustment board 104 like beads.
FIG. 11 is a sectional side elevation showing the background-art optical pickup device of FIG. 10. In FIG. 11, constituent elements identical to those of FIG. 10 are represented by the same reference signs. Further, reference signs 104a and 105a represent light-transmitting holes, and a reflected light 108 from a not-shown optical disk enters the optical detector 101 through the light-transmitting holes 104a and 105a. 
The optical detector receives the reflected light 108 from the optical disk and outputs the information recorded on the optical disk as an electrical signal. Further, the optical detector also detects the misalignments of a light spot relative to the optical disk in a focus direction and a tracking direction and outputs the information of misalignment as an electrical signal. The information on the misalignments of the light spot is inputted to a not-shown objective lens actuator and used for a correction of the position of the light spot.
It is necessary to accurately focus the reflected light 108 on a light receiving surface of the optical detector 101 and therefore fix the optical detector 101 to a position adjusted relative to the optical unit 105 with high accuracy.
In the background-art process of manufacturing the optical pickup device, since the optical detector 101 is already soldered onto the FPC 102 attached onto the adjustment board 104 at the time of position adjustment, the position adjustment of the optical detector 101 is performed by moving the adjustment board 104 on which the optical detector 101 is fixed relatively to the optical unit 105. Usually, this position adjustment is performed while the electrical signal outputted from the optical detector 101 is observed through the FPC 102, and the optimal position of the optical detector 101 is determined on the basis of the electrical signal.
After determining the position of the optical detector 101, a small amount of first adhesive 106 is applied between the adjustment board 104 and the optical unit 105 and hardened by short-time ultraviolet irradiation. Further, the second adhesive 107, i.e., the two-part epoxy, is applied and slowly hardened, taking a time ranging from several minutes to several hours, to fix the adjustment board 104 to the optical unit 105.
In the above case of position adjustment of the optical detector 101, however, since there is a large friction between the adjustment board 104 and the optical unit 105, it is hard to make a fine adjustment thereof and therefore difficult to improve the accuracy in position adjustment.
Further, in a case of optical pickup device having a plurality of light receiving unit rows on the optical detector 101 and receiving a plurality of luminous fluxes by one optical detector 101, it is necessary to perform positioning of the optical detector 101 in the direction of rotation about the optical axis direction of an incident light of the optical detector 101 with high accuracy. Also in this case, because of large friction, it is difficult to improve the accuracy of position adjustment.
Furthermore, as discussed above, the adjustment board 104 and the optical unit 105 are fixed to each other with the adhesive after completion of the position adjustment of the optical detector 101 in the background art. Because of the temperature characteristic of the adhesive and shrinkage in hardening, the position of the optical detector 101 varies when the adhesive is hardened and this causes deterioration of reliability in position of the optical detector 101 after adjustment.